1. Field of the Invention
The present invention relates to a small push button switch having a housing which is formed in such a manner that a belt-like metallic plate is inserted in the housing. This belt-like metallic plate serves as a basic material of a fixed contact or a terminal of the push button switch.
2. Description of the Related Art
FIG. 8 is a plane view showing a housing of this kind of push button switch as a related sample. In the drawing, a push button switch comprises a housing 1 formed by being inserted two belt-like metallic plates 2, 3 extending in parallel with each other. The housing 1 has a rectangular configuration when seen from the top, and has opening 1a therein. At an inner bottom surface of the housing 1, there is exposed a central fixed contact 4 and a circumferential fixed contact 5 so as to be spaced with each other.
The central fixed contact 4 is made of a part of one belt-like metallic plate 2, to the contrary the circumferential fixed contact 5 is made of a part of the other belt-like metallic plate 3. Both end portions of each belt-like metallic plate 2 or 3 are formed in a terminal shape by being bent to serve as a terminal, respectively. That is, the belt-like metallic plate 2 or 3 has a pair of projecting portions protruding from an outer wall surface 1b of the housing 1 in opposite directions with each other.
These projecting portions are to serve as terminals 6 or terminals 7 in the drawing. Each terminal 6 or 7 has a stepped portion 6a, 7a, each being bent in a cranked-shape along the outer wall surface 1b of the housing 1. A distal end of respective terminal 6 or 7 protruding from each stepped portion 6a or 7a is a part serving as a soldering part. That is, this soldering part is soldered at predetermined position of a printing circuit pattern substrate.
Furthermore, there is provided a movable contact formed in a dome-shaped configuration (not shown). This movable contact is disposed on the circumferential fixed contact 5 so that a central part of the movable contact can be pushed downward to contact with the central fixed contact 4. Thereby, both fixed contacts 4 and 5 can be electrically associated to conduct an electricity by manipulating the movable contact. Namely, the switch is changed its condition from an OFF-condition to an ON-condition.
In such a push button switch, the belt-like metallic plate 2 or 3 penetrating the housing 1 is cut into a predetermined shape through a press processing and, in turn, is inserted into molding dies with keeping its hoop-condition so as to be integrated with a housing 1.
In the case that the push button is made small, a thickness of the belt-like metallic plate 2 or 3 serving as a basic material for the fixed contacts 4, 5 or the terminals 6, 7 becomes thin. Usually its thickness is a level of 0.1 mm. Therefore, this thin belt-like metallic plate 2 or 3 is likely to be deformed by the pressure of melted resin when it is inserted into the housing during the molding operation. As a result, it was feared that the fixed contacts 4 and 5 do not protrude a predetermined amount on the inner bottom surface of the housing 1 and, consequently to fail performing a switching operation to conduct an electricity.
Moreover, it is desirable for this kind of button switch to reduce a protruding amount of each terminal 6 or 7 with respect to housing 1. However, it is also necessary to keep a sufficient area for a soldering operation more than a predetermined area at a front end portion of each terminal 6 or 7. Thus, it was not possible to reduce the protruding amount of each terminal 6 or 7 by a large amount at once. Accordingly, the maximum span of the belt-like metallic plate 2 or 3 results in becoming fairly larger in size than the maximum outer radius of the housing 1 of the same direction. And thus, it was difficult to provide a desirably compact button switch in size.